It is hovercraft smooth and has buckets of thrust, banging out 0-60mph in four seconds

I must stress this is the prototype — hand-built, one of one, worth £1million-plus — so I wasn’t tooling around.

But I can tell you it is hovercraft smooth and has buckets of thrust, banging out 0-60mph in four seconds.

You want more numbers? OK, it has twin electric motors producing 400hp and 700 Nm of torque. That’s exactly the same torque rating as the F-Type SVR.

And this is a cheerleader for the polar bear preservation unit, remember, not a flame-spitting V8. And the range? Tesla territory. Up to 310 miles with an 80 per cent charge in 90 minutes.

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There's also plenty of room inside

Hmmm. Not quite there yet, is it?

Charge time is still the Achilles heel for electric cars, as well as the lack of charging points. But all that will change in time. Other observations. The I-Pace cabin is predictably brilliant. As quiet as a library.

Jaguar's electric vehicle is expected to combine a long distance range of more than 500km

And because there are no oily bits it has plenty of S, P, A, C and E. Room for five and all their luggage. It also blends modern equipment (three display screens, huge glass roof) with lots of little nods to Jaguar’s heritage, including “Jaguar, Coventry, Est. 1935” on seat labels and the walnut dash.

Tesla can’t play that card.

Jaguar's first electric car, the I-PACE Concept unleashed onto the streets of London for the first time

Design boss Ian Callum said: “This is the start of a new era for Jaguar. Transportation will change more in the next ten years than it has in the past 50 years and we’re prepared for that change.”

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The I-PACE is expected to be officially revealed late this year

He’s right too. And he’s hit the target with his first shot.

Keyfacts: JAGUAR I-PACE

Price: £60,000

Power: 100% electric (two motors producing 400hp)

0-60mph: 4 secs

Top speed: 120mph

Range: 310 miles

Charging: 80% in 90 mins

Out: 2018

The I-Pace will be revealed in production spec in September and will hit showrooms in 2018, priced around £60,000.